IS 1 VACCINE DOSE ENOUGH ?

Researchers found that those who did not have COVID-19—called COVID naïve—did not have a full immune response until after receiving their second vaccine dose, reinforcing the importance of completing the two recommended doses for achieving strong levels of immunity.

The study provides more insight on the underlying immunobiology of mRNA vaccines, which could help shape future vaccine strategies.

“These results are encouraging for both short- and long-term vaccine efficacy, and this adds to our understanding of the mRNA vaccine immune response through the analysis of memory B cells,” says senior author E. John Wherry, chair of the department of systems pharmacology and translational therapeutics at the University of Pennsylvania and director of the Penn Institute of Immunology in the Perelman School of Medicine.

The data show key differences in vaccine immune responses in COVID naïve versus COVID-19 recovered people. The findings suggest that only a single vaccine dose in people recovered from COVID-19 may be enough to induce a maximal immune response, based on both strong antibody and memory B cell responses. This is likely due to a primary immune response because of their natural infection.

Although more data are needed and all subjects developed robust immunity, it is possible that inflammation and side effects early after vaccination could signal stronger immune reactions.

“Everyone has good responses to the vaccines. They work to protect people against COVID-19. But for those who may be worried about side effects, they are not necessarily a bad thing—they may actually be an indicator of an even better immune response,” Wherry says.

The researchers are continuing larger-scale studies, which are necessary to fully examine the question of a one- or two-dose regimen in COVID-19-recovered people and to see how long the vaccine antibodies last. Wherry and his team are continuing to study the vaccine’s effect on virus-specific T cell responses, another element of the body’s immune response.

The human immune response to vaccines and infections result in two major outcomes—the production of antibodies that provide rapid immunity and the creation of memory B cells, which assist in long-term immunity. This study represents one of the first to uncover how memory B cell responses differ after vaccination in people who previously experienced infection, compared to those who have not had COVID-19.

“Previous COVID-19 mRNA vaccine studies on vaccinated people focused on antibodies more than memory B cells. Memory B cells are a strong predictor of future antibody responses, which is why it’s vital to measure B cell responses to these vaccines,” Wherry says. “This effort to examine memory B cells is important for understanding long-term protection and the ability to respond to variants.”